Rooftop Crane Lift with a Corroded Curb
A crew is replacing a 5-ton packaged rooftop unit and supply plenum on a two-story, 28-ft office building. The crane is scheduled for 7:00 a.m., and the forecast calls for sustained wind at 18 mph with gusts to 28 mph. The roof is low-slope with no parapet; the access hatch is about 20 ft from the roof edge. The old unit is still energized, and a gas line runs within 3 ft of the rusted roof curb. While inspecting the curb, the lead installer finds that one corner has rusted through and the curb is not square. The crew plans to rig the old unit and set the new unit in a single crane pick to save time. The general contractor has not issued a lift plan or a job hazard analysis for the roof work. Two apprentices are on site, and one has not completed fall-protection training.
1. What should the lead installer do before any rigging begins? Identify the immediate stop-work issues and the required controls.
Read the worked answer
Stop the lift until the hazards are controlled. The gust forecast likely exceeds the crane manufacturer's wind limit, there is no lift plan or JHA, the roof edge lacks fall protection, the old unit is energized, and the curb is structurally compromised. Require a coordinated lift plan and JHA; verify the crane load chart, rigging, and wind limit; establish an exclusion zone; provide edge protection or personal fall arrest with a suitable anchor; lock out/tag out the electrical circuit and have the gas utility isolate the gas line; and keep untrained apprentices off the roof. Do not rig until the GC, crane operator, and qualified persons agree the lift can proceed safely.
2. How should the rusted curb, gas line, and electrical hazard be handled before the new unit is set?
Read the worked answer
The curb is part of the structural support and cannot be left with a rusted-through corner. Remove the old unit, inspect the roof deck and curb, and repair or replace the curb so it is square, level, and capable of supporting the new unit and curb adapter. Protect the gas line from the load and maintain required clearance; have the utility isolate and lock out the gas, and never use gas piping as a support. Disconnect and lock out the electrical feed, verify zero energy, and protect the conduit and disconnect. Photograph the conditions and obtain GC approval before setting the new unit.
3. What should be documented and communicated to the GC and crew before work resumes?
Read the worked answer
Document the stop-work decision, the crane wind-limit check, the revised lift plan and JHA, the fall-protection plan, electrical and gas lockout permits, the curb repair approval, and the training status of each worker. Hold a tailgate meeting with the crew and crane operator, review the sequence and exclusion zone, and confirm stop-work authority. Notify the GC in writing of the required corrections and the revised schedule, and retain inspection photos and sign-off before any pick is made.